Heretofore, various types of valve assemblies have been contructed for the primary purpose of controlling the flow of pressure air or other pressure fluid to opposite ends of a cylinder assembly and with porting for controlling the flow of exhaust out through the valve assembly. An example of such prior art contruction is shown in U.S. Pat. No. 3,017,901 entitled "Valve Assembly".
In that contruction within the bore of the body there is provided a series of rings 32, a series of spacers 34 and seals 36 in conjunction with valve stem guides 38 with central bores all to define together, a bore within which is movably mounted the valve spool. The objection to such contruction is that it is highly complicated and costly to maufacture and is too complex. One purpose for the use of such ring spacers, seals and valve stem guides was to allow greater tolerance between the diameter of the rings and the valve body sealed with the O-rings, and providing for operation of the spool despite some distortion of the body.